Cloud storage services like Dropbox are incredibly convenient, but that convenience comes with a price: your data is stored in a place where others can get at it, and the only things preventing that from happening are the service's own security and privacy policies and practices. It's also costly to keep large amounts of data in sync—most services will give you a few gigabytes for free, and then charge monthly or yearly fees for larger quantities.

Some services, like SpiderOak, attempt to address the security problem by removing themselves entirely from the encryption process and ensuring that they never have access to the keys to your data, but storing more than documents still requires an investment in relatively expensive server-side storage (and as we noted in our review, the service's interface leaves a bit to be desired). Some other vendors offer "personal cloud" services which allow you to access your local files from elsewhere, but these can lack the OS integration and ease-of-use which the ubiquitous Dropbox presents.

If you're looking for something that will let you use your own server for storage and looks and acts pretty much like Dropbox, AeroFS might be for you. The service is still in an invite-only beta as of this writing, but with just a few additions it could be the locally hosted Dropbox that some Windows, OS X, and Linux users have waited for.

Basic operation

After getting your invite and downloading the software, you'll be prompted to create an account. This sign-in exists only so that your Aero FS-running computers can get the 2048-bit RSA encryption keys keys they need—your computers then authenticate against each other using these keys, and can do so even if the AeroFS servers are down. Your data is fully encrypted before being transferred to other computers, preventing it from being intercepted and decoded in transit.

Installing the AeroFS software creates a folder in your user profile, much like Dropbox does, and this can be changed from the default location as desired. In both Windows and OS X, AeroFS automatically adds a link to your shared folder in the Favorites section of the Windows Explorer and Finder, respectively. Once you've installed AeroFS on more than one system, everything placed in this folder is automatically propagated to all of your other AeroFS-linked computers.

The AeroFS menu gives you access to version history, folder sharing, and other preferences and settings.

Aside from the security advantages of keeping all of your file syncing and data transfers local (once you've installed the AeroFS software and authenticated, an Internet connection is no longer required), AeroFS frees you from the limited amount of storage space provided by other cloud service vendors. The size of your "personal cloud" is limited only by the amount of disk space on your various computers.

If you've got a computer with a small hard drive and only want to sync some of your AeroFS contents, it's easy to configure Selective Sync from within the GUI.

Limiting download and upload bandwidth is also possible, which is especially desirable if you're syncing between multiple clients.

Sharing files between AeroFS users is slightly more complicated than with Dropbox, but it's still not difficult. First, click the AeroFS tray icon, click Share Folder, and select the folder you'd like to share.

Shared folders appear with an icon overlay to differentiate them from standard folders.

You'll then be presented with a dialog box with a customizable message asking for an e-mail address to share with. That person will then be sent an eight-character code; on the receiving end, you click the AeroFS tray icon again, click "Accept Invitation," and input the code to gain access to the shared folder.

Shortcomings

The sync and sharing features work and work well, but that's the easy part—Dropbox also has fairly robust versioning, deals with conflicting files reasonably seamlessly, and lets you access your files from just about anywhere, including your Web browser, smartphone, or tablet of choice.

The versioning system in AeroFS is also perfectly usable—click "Version History" in the tray icon menu and you can go through all of your files and folders to see their previous versions. AeroFS will keep storing older versions as long as there is sufficient free local disk space; if your disk gets too full, it will begin silently deleting the very oldest items to make more room.

AeroFS' versioning system keeps old versions until it runs out of space, and then begins deleting the oldest copies of files to make more room.

One thing that doesn't work quite as well is the way AeroFS handles file conflicts. To test this, I created a text file, typed some information into it, and saved it to my AeroFS folder. To make sure syncing was working, I opened up the document on one computer at a time and typed in additional text—sure enough, the changes would propagate to each system pretty much instantly as I made edits.

Then, I paused syncing on both systems, made more changes to the text file on each system, and then re-enabled syncing. Each system would continue displaying notifications as I made changes, giving me the impression that my changes were being sent out, but in reality each computer was treating its version as the definitive version. I could find the other computer's copy of the file in the Version History window, but otherwise there was no indication that anything was wrong.

I didn't lose any data because of this—both versions of the documents were still present on both computers. But where Dropbox automatically creates a separate version of the file and renames it to indicate which of your systems it came from, AeroFS simply behaves as if everything is working as it should. This could be a problem if all of your systems aren't always on at the same time—it's not something that's likely to happen if you have an always-on "server" running AeroFS, but conflict management is a major concern in any file syncing solution, and AeroFS's could be better.

And finally, we get to AeroFS's biggest shortcoming, which is lack of access from Web browsers or mobile devices. Dropbox (and, for that matter, Google Drive, SugarSync, Box.com, and most of the other major players in this field) offers apps for iOS and Android as well as a robust Web client that can be used to access your files while on public computers. There are probably ways around this problem—an intrepid DIYer could probably set up a WebDAV server pointed at their AeroFS folder to enable Web and mobile access—but it's too bad that such a major piece of functionality is missing from the main package.

Conclusions

AeroFS is still in beta, and the problems we had with it may well be ironed out by the time it's actually ready for public release. As it stands, the product works best if you're a security-minded individual or small business with a server dedicated to synchronizing files among many clients. The software can also be used at home to synchronize files between, say, a desktop and laptop that aren't always on at the same time, but the conflict management problems we had might cause problems if you're not careful.

When things are working, though, AeroFS provides an experience that's nearly as seamless and simple to explain as Dropbox, but with the added security that comes from keeping your data (and data transfers) confined to your devices rather than on someone else's server. The level of OS integration present and its ease of configuration make it one of the most promising "personal cloud" solutions we've seen so far.

Owncloud is open source and includes media streaming, sharing, photo galleries, calendar synch etc. And is a better experience imo. There is enterprise support, but the community version is where most people go and I love it. Also, very nice simple ios app.

If you want local, private sync and mobile apps for all the platforms (iOS, Android, Blackberry and Windows 7.5) take a look at Tonido Sync (http://www.tonido.com/app_sync_home.html). It is a very mature solution and has web interface as well.

If you want local, private sync and mobile apps for all the platforms (iOS, Android, Blackberry and Windows 7.5) take a look at Tonido Sync (http://www.tonido.com/app_sync_home.html). It is a very mature solution and has web interface as well.

Beat me to it, and they also have a low-power hardware based solution as well.

Owncloud is open source and includes media streaming, sharing, photo galleries, calendar synch etc. And is a better experience imo. There is enterprise support, but the community version is where most people go and I love it. Also, very nice simple ios app.

It is also probably the buggiest POS you will ever use. Don't get me wrong, I am following it avidly, waiting and hopeful that someday soon it will actually be useable. But as of now it breaks way to easily to be used by those without a lot of patience and willingness to fix the numerous bugs they will run in to themselves.

I use Windows Live Mesh to sync large folders and stuff I don't want MS looking at, although I'm not sure if this is comparable and how much of my data is going through Microsoft's servers. Although it can be buggy and I lost half my music collection before, so I make sure to back up my files before synching a new folder location.

I quite liked Crash Plan when I gave it a try; it lets you do local syncing of a sort, as well as backing up to their cloud storage (or your own servers). It's not really a syncing tool as such, but it lets you specify your own encryption keys like SpiderOak etc.

That raises a question actually; one of the things Crash Plan lets you do is specifying your own key manually, leaving it up to you how to protect it. Does AeroFS allow this option as well or does it have to store the key on their servers?

Maybe its just me -- but can't all this be done with the combination of cron and rsync?? Why do I need a third party to give me a feature I already have? Kind of seems like these services are re-inventing the wheel on services that long been in existence for a long time --- if local syncing is what you are after!

This looks very promising from a versioning perspective. I'm looking for a good, transparent, local versioning system. I use Time Machine but it's 1-hour time between backups tends to leave a lot of holes. I work with a bunch of audio software, some of which has dubious undo histories, so I'm definitely looking for something more frequent. Because I'm doing audio work, I end up with very large files, so Dropbox is not a great solution for me.

Does anyone have any versioning suggestions or have an invites to AeroFS? I'm using Mac OS X Mountain Lion 10.8.2 Cheers!

Maybe its just me -- but can't all this be done with the combination of cron and rsync?? Why do I need a third party to give me a feature I already have? Kind of seems like these services are re-inventing the wheel on services that long been in existence for a long time --- if local syncing is what you are after!

rsync is certainly the simplest option if you can be bothered setting it up and that's all you want. More complex features like conflict detection/resolution can be very handy though, and I'm not sure rsync can handle that situation desperately well?

If you know you're only using one device at a time though then rsync is just fine as you say, and there are some decent GUIs out there for it.

Isn't part the whole point of Dropbox, etc to be able to access your documents from anywhere? Synchronizing is important, but if you are limited to your home network, then might as well use a USB stick. I always thought that the benefit of Dropbox was that I could be off at a meeting, and could log onto my Dropbox account to access my documents knowing that they were all the up to date versions. I don't see how most of these other options give that ability (perhaps I'm missing the point here, so feel free to correct me...)

I have been trying to figure out whether something like a QNAP or Synology system might be a good alternative, but they seem to be only FTP access - I prefer the clean interface of Dropbox, and the like. Any suggestions?

How well does it deal with swapping between internal and external networks? That is, how well does it cope between talking to other devices within a home network (e.g. desktop and laptop on the same 192.168.x.x network) compared to when I take the laptop elsewhere and connect to the net at a friend's house?

I guess I'm asking "How well does it cope with NAT?" Will my laptop be able to connect through a NAT to my desktop without portforwarding? How does it cope with syncing to multiple machines behind a NAT? (e.g. My laptop at a friend's house syncing to my home desktop and HTPC.)

Owncloud is open source and includes media streaming, sharing, photo galleries, calendar synch etc. And is a better experience imo. There is enterprise support, but the community version is where most people go and I love it. Also, very nice simple ios app.

It is also probably the buggiest POS you will ever use. Don't get me wrong, I am following it avidly, waiting and hopeful that someday soon it will actually be useable. But as of now it breaks way to easily to be used by those without a lot of patience and willingness to fix the numerous bugs they will run in to themselves.

Agreed. I'm running ownCloud on a FreeBSD server at home, and it's been a pretty painful experience so far. The specs and features look great, but the reality is really sub-par. It only became (mostly) usable since version 4, but I've found it so unreliable that I'm still using Spideroak for the things I don't want to lose.

And the clients! Bleah! Don't get me started! Yeah, sure the time difference is too great to sync between machines

Yet, like a sucker, I'm also following it avidly, hoping that one day it'll be good enough to use exclusively.

What I want to know is, what is their business model? They've got 14 employees so they're obviously planning to make money off this somehow, but nothing on their site indicates how they plan to do this. This seems to me like pretty important information if they expect me to trust them to handle my data.

Anyone used SparkleShare http://sparkleshare.org/ ? Open source and multi platform (don't think that includes mobile apps though, but probably through the browser). I'm guessing there are some features its lacking that I'm not seeing compared to these other programs?

Don't understand why there are comments effectively saying, 'oh oxygencloud does this' or 'cubby does that'. They don't. With AeroFS you have unlimited storage and you don't have to trust your files on anybody else's server.

I've been experimenting with OwnCloud myself. It seems to do most of what Mesh used to do, but the drawback is that files in the cloud are unencrypted and visible to the sysadmin. Also I can't find a way to designate a folder 'network only' so that it is mapped to devices locally but only accessible when they have a network connection(data being stored entirely server side).

I have for a little while as well, but I didn't get as far as you did. I found it WAY too buggy to have any confidence that it's robust enough to trust my files to.

Version 3 would only connect intermittently, usually giving an error about how the system time was too far off to connect properly (this was on a lan with both machines updating their clocks to the same NIST server, meaning there was never more than 2 seconds difference between them). When updating from version 4.0.1 to 4.0.8 it wiped my user accounts and associated files (I only had two accounts in there, but still). This is running on a FreeBSD 9 machine, fully updated.

Since I'd be using it to store my files on my machine, I'm not as concerned about encryption as I'd be if they were stored on somebody else's computer, but it'd be a nice touch.

OwnCloud 4.5 is running much better than previous versions, but it's going to be a while before I trust it too much.

OwnCloud 4.5 is running much better than previous versions, but it's going to be a while before I trust it too much.

OwnCloud is still buggy. Client software doesn't even need second computer to stuck in conflicts. It can't sync changes too often and you should spend your time to fix syncing.

5.0 was just released and supposedly has significant improvements. I've found it to be a neat idea that simply needs more work. I'd like to at least make it trustworthy for backup operations, but I don't trust it that far yet.

OwnCloud 4.5 is running much better than previous versions, but it's going to be a while before I trust it too much.

OwnCloud is still buggy. Client software doesn't even need second computer to stuck in conflicts. It can't sync changes too often and you should spend your time to fix syncing.

5.0 was just released and supposedly has significant improvements. I've found it to be a neat idea that simply needs more work. I'd like to at least make it trustworthy for backup operations, but I don't trust it that far yet.

They have been saying that the next release will actually be usable on every release though. I followed from 2.0 to 4.5, and it was always just an unusable pile of steaming crap. Maybe they did finally get the magic bullet on the 5.0 release, but somehow I doubt it.

OwnCloud 4.5 is running much better than previous versions, but it's going to be a while before I trust it too much.

OwnCloud is still buggy. Client software doesn't even need second computer to stuck in conflicts. It can't sync changes too often and you should spend your time to fix syncing.

5.0 was just released and supposedly has significant improvements. I've found it to be a neat idea that simply needs more work. I'd like to at least make it trustworthy for backup operations, but I don't trust it that far yet.

They have been saying that the next release will actually be usable on every release though. I followed from 2.0 to 4.5, and it was always just an unusable pile of steaming crap. Maybe they did finally get the magic bullet on the 5.0 release, but somehow I doubt it.

I wouldn't go that far. It has improved tremendously. Its just not there yet.

I followed from 2.0 to 4.5, and it was always just an unusable pile of steaming crap. Maybe they did finally get the magic bullet on the 5.0 release, but somehow I doubt it.

I upgraded to 5 not long after it came out. There was a bug that initially seemed to break the install, but after searching the forums I found the fix (manually editing a php file) and it upgraded everything successfully.

It's no magic bullet, but 5 is a version I'm actually going to start using full time. I don't yet trust it, but I have to start somewhere, so I'm using it to sync non-crucial things like funny pictures I find on Reddit or music I rip from my CDs (stuff I can replace). I kinda want to see a history of it working before I use it for anything else.

But I'll definitely agree that 3 and 4 were unusable piles of crap. I am impressed by the rate of development, though. It doesn't feel like it was that long ago I was first trying out 3.